Ring rolling mills



July 24, 1962 Filed March 10, 1959 N. c. ASHTON ETAL 3,045,516

RING ROLLING MILLS 2 Sheets-Sheet l nvvE/v TokS Y Mum A TTORNE. 7

July 24, 1962 N. c. ASHTON ETAL 3,045,516

RING ROLLING MILLS Filed March 10, 1959 2 Sheets-Sheet 2 o 0 es 112, 2 I0 AVMENTORQ QEGM.VWWQ5V MULSON ATTORNEY 3,045,516 Patented July 24, 1962 Ring rolling mills are designed to form rings or short cylinders from annular blanks which are of substantially the same axial length but of greater radial thickness and smaller in diameter than the desired dimensions of the ring or short cylinder to be produced therefrom. A ring rolling mill usually comprises a table to support the blank during rolling, a driven roller rotatably mounted at a Vertical axis on the table, and a pressure spindle or roller which is freely rotatable about a vertical axis and is carried by a member movable horizontally towards and away from the driven roller, means being provided for urging the pressure spindle or roller towards the driven roller. In use, a heated annular blank is placed over one of the rollers, and then the pressure roller is moved towards the support roller which serves to progressively reduce the radial thickness of the blank and at the same time increase its diameter.

One of the disadvantages of ring rolling mills as described above, is that rings or short cylinders formed thereon usually depart from true circles to such an extent that substantial tr-ueing and/ or machining operations are necessary before they can be used. Such rings which have required substantial trueing tend to become distorted if they are subsequently subjected to successive heating and cooling, such as occurs to rings incorporated in gas turbine engines.

It is known to provide a ring rolling mill with control rollers which are intended to engage with the ring on opposite sides but as the ring is continually increasing in outside diameter during the rolling process, it is necessary to provide for continuous adjustment of these control rollers as rolling proceeds.

This adjustment is done manually or by means of a cam operated control gear, and not only requires skilled labor, but is not accurate, and does not usually produce rings of good circularity.

The present invention is designed to provide a method of ring rolling and a ring rolling mill which is capable of forming rings or short cylinders of greater accuracy than can be formed on previously known ring rolling mills. Consequently trueing and machining operations will be substantially reduced and this in turn will reduce the risk of subsequent distortion.

The invention is based upon the discovery that throughout the ring rolling process if truly circular rings are being formed, there are two positions on the periphery of the ring which do not move relatively to the support roller axis, despite the changes in the thickness and diameter of the ring.

This can be proved mathematically as follows:

Let the internal radius of a ring he a and its outside radius b. The general formula for a circle of radius a and which has a diameter on the ordinate y and passes through the origins is x (y|a) :a (where y is the ordinate at the position x). And for a concentric circle of radius [2 the general formula is Now in the ring rolling process, where the axial length of the ring does not change:

where A is a constant for any given ring and is in fact the area of the annular cross section of the ring.

Therefore Substituting this in the Formula 1 we have:

1r$ +1r(y+a) =A+-1ra In the case where y=0 (i.e. where the abscissa x is a horizontal tangent to the small circle whose radius is a) this reduced to:

Therefore x is expressed in terms of the constant A and is completely independent of the radii a and b.

Stated another way, it can be said that if one point on the periphery of the inner circle remains stationary during a change in the size of a ring (which change must comply with the ring rolling condition of no change in axial length) the periphery of the outer circle will always pass through those points on the tangent to the stationary point which are spaced from the said stationary point by a distance equal to 'II" There are, of course, two such points, one on each side of the stationary point.

Now the ring rolling process complies with all the necessary conditions of this mathematical proof, as the axial length of the ring does not change, and the point at which the ring contacts the support roller remains fixed throughout the rolling process provided that the support roller rotates about a fixed axis. It follows, therefore, that for any given ring to which ring rolling is applied, there are two points on its periphery which do not alter their positions relatively to the support roller axis.

According to this invention, therefore, a method of forming a ring or cylinder from an annular blank on a ring rolling mill comprises applying radial pressure to the blank between two parallel rollers, one of which engages with the inner surface of the blank, and the other engages with the outer surface of the blank, one of the said rollers being rotated, and at the same time engaging a control member with the periphery of the blank along an axial line generally parallel to the axis of rotation of said blank and which is in a plane containing a tangent to the inner roller at the point Where the inner roller engages with the blank, the control member being so positioned relatively to the axis of the inner roller that its axial line of engagement with a circumference of the blank is at a position which does not move relatively to the axis of the inner roller throughout the rolling process.

As mentioned previously there are two points on the circumference of any blank at which the control member could be positioned, and there are at least three ways in which the invention can be carried out. These are:

(1) To provide two control members equally spaced one on each side of the plane passing through the axes of the inner and outer rollers, in which case the point of contact of each control member with the blank will be spaced from this plane by a distance equal to where A is the annular cross sectional area of the blank.

3 (2) To provide two control members one on each side of the plane passing through the axes of the inner and outer rollers, the control members being unequally spaced from this plane, but spaced from each other by a distance equal to where A is the area of the annular cross section of the blank. This is obviously not so good as the first method, because the apparatus is assymetrical and the loads on the control members will not be equal.

(3) To have only one control member positioned on one side of the plane passing through the axes of the inner and outer rollers, the control member being spaced from this plane by a distance equal to A where A is the area of the annular cross section of the blank. This method relies upon the nipping effect of the inner and outer rollers to oppose any force tending to move the ring away from the control member. It is obviously not so good as the first method and would probably be successful only if the control member were positioned on the approaching side of the inner and outer rollers (considering the direction in which the ring rotates during the rolling process).

According to a preferred feature of the invention, apparatus for carrying out the method according to the invention comprises a ring rolling mill having a support roller and a pressure roller movable towards the support roller, a driving mechanism for rotating either the support roller or the pressure roller, and two control members adjustably mounted one on each side of the plane containing the axes of the support and pressure rollers, the control members being adapted to engage with a blank on the mill along axial lines generally parallel to the axis of rotation of the blank and which are in the plane tangential to the support roller at the line where the blank engages on the support roller.

Conveniently the control members may be rollers freely rotatable in bearings which can be secured relatively to the axis of the support roller. Alternatively, rods or the like may be provided instead of rollers for this purpose. It will be appreciated that for extreme accuracy, the control members should have knife edge contact with the blank, but this is impracticable in view of the loads which the control members have to withstand. In practice it is found that a small diameter roller gives quite satisfactory results.

The construction arrangement and method of operation of a ring rolling mill in accordance with the invention will now be described by way of example only, with reference to the accompanying drawings, in which:

FIGURE 1 is a side view of the mill;

FIGURE 2 is a front view of the mill;

FIGURE 3 is a detail view of some of the rollers with a ring in the process of being rolled;

FIGURE 4 is a side view of the rollers shown in FIG- URE 3 without the ring,

FIGURE 5 is a diagram of the hydraulic circuit, and

FIGURE 6 is a partly sectional plan view of a control roller mounting.

The mill has a base plate 10 and a steel framework 12 on which the various moving parts are mounted. It should be mentioned here that the mill shown in the drawings is a prototype, and that it might be found more desirable to construct the general framework of the mill from large castings to give additional weight and rigidity.

At the rear end, an electric motor 16 is mounted upon a base plate 14, and is adapted to drive a driving shaft 18 through a belt drive 20 and a worm gear reduction box 22. The driving member 24 of a clutch is fixed on the driving shaft 18 and the driven portion 26 of this clutch is slidably keyed on a driven shaft 28 arranged co-axial with the driving shaft 18. The clutch is adapted to be operated by means of a hand wheel 30 controlling a screw 32 on which there works a nut 34 fixed to the end of a lever 36, which, through a second lever 38, is connected to a toggle mechanism 40, so that by turning the hand wheel 30 the toggle mechanism 48 is made to slide the driven portion 26 of the clutch into or out of engagement with the driving portion 24. The clutch arrangement, therefore, provides a means whereby the driving shaft 18 can be coupled directly to the driven shaft 28 and can thus provide rotary motion for the driven shaft 28.

At its front end, the driven shaft 28 projects through a plate 42 fixed to upright members of the frame 12, and carries a support roller 44. This support roller 44 is one of the two rollers used for squeezing the blank, and in FIGURE 2 a ringed blank is indicated by the chain dotted lines 46, and it will be noted that the blank rests on the circumference of the support roller 44.

Above the support roller, a pressure roller 48 is freely rotatably mounted in a bearing 50 which is slidable vertically on a guide 52 formed on a plate 54 fixed to the upright members at the front of the framework. This pressure roller 48 is the other roller used in the squeezing action, and it should be noted that the axis of the pressure roller is vertically above the axis of the support roller. Means are provided for raising and lowering the bearing 5%, these means comprising a hydraulic ram 56, the cylinder 58 associated with the ram being carried by cross members 60 forming part of the machine framework. A pump 62 is mounted within a reservoir 64 and is adapted to be driven by means of an electric motor 66 through a belt 68. This pump supplies the operating liquid under pressure to the cylinder 58 through a two way control valve 70.

The hydraulic circuit is shown in FIGURE 5 of the drawings, and will now be described. Operating liquid under pressure from the pump 62 is forced through the line 72 into the two way valve 70, and if this valve is set to move the ram 56 downwardly, the liquid under pressure passes through the line 74 to the upper end of the cylinder 58. At the same time a return line is opened through the line '76 which leads from the lower end of the cylinder 58 to the control valve 70, and a line 78, which leads from the control valve back to the reservoir 64.

A trip lever is pivoted on the mill framework 12 and is connected through a rod 82 to a release valve 84, and the arrangement is such that when the pressure roller has been lowered to a predetermined position, the trip lever 80 operates the release valve 84, and opens a return line from the pressure line 74 through a line 86 back into the line 78 and thence back to the reservoir 64. This lever 80 therefore provides a means whereby the movement of the pressure roller 48 towards the support roller 44 can be limited, and it will readily be appreciated that by providing some means of adjusting the connection between the trip lever 80 and the rod 82 (such, for example, as a nut fixed on the lever 80 engaging with a screwed part of the rod 82) it is possible to adjust the position at which the release valve 84 will be opened to stop the downward movement of the pressure roller 48.

When it is desired to raise the pressure roller 48 the two way valve is reversed, and liquid under pressure from the pump 62 passes through the line 72, thence through the valve 70, and line 76 to the lower end of the cylinder 58. At the same time a return line is opened through the line 74, valve 78 and line 78.

A pair of brackets 88 and 90 project one on each side of the front end of the mill, and these brackets carry control roller arrangements which are identical excepting that they are of opposite hand, and therefore it is only necessary to describe one of these units in detail.

A control roller 92 (which in this particular instance is a hardened steel roller of about four inches diameter) is freely rotatably mounted in a bearing block 94, which is slidable horizontally on the front face of the bracket 88. The mechanism for controlling the sliding movement of the bracket 94 is similar to that provided for. the centre of a lathe tailstock, and comprises a sleeve 96, slidable axially within the bore of a block 98 which is fixed to the bracket 88, the sleeve having a nut 100 which engages on the screwed portion 102 of a spindle 104, the spindle having also fixed on it a disc 106 which is engageable either with the bottom of a counter bore 108 in the outer end of the block 98, or with the inside face of an end plate 110' fixed on the outer end of the block 96. By rotating the spindle 104, in one direction, the disc 106 engages with the inside face of the end plate 110, and further rotation of the spindle causes the sleeve 96 to move inwardly. If the spindle is rotated in the opposite direction, the disc 106 engages with the bottom of the counterbore 108, and thereafter continued rotation of the spindle causes the sleeve 96 to move outwardly. The spindle 104 is provided with a handwheel 112 whereby it can be readily rotated manually. A locking handle 113 is provided on the block 98, and this handle is made to operate a clamping device (not shown) which acts on the sleeve 96 in similar manner to the locking devices provided on many machine tools, such as for instance the locking device provided for the sleeve of a lathe tailstock.

In order to provide some added measure of control over the movement of the roller carrying block 94, a face plate 114 is fixed to the end of the block 94, and is slidable on the face of the block 98. A pair of screws 116 and 118 extend through a longitudinal slot 120 in the plate 114, and are secured in screwed holes in the block 98. By slackening the screws 116 and 118, it is possible to move the plate 114 relatively to the block 98 as is required when the sleeve 96 is moved by rotation of the handwheel 112. When the sleeve 96 has been locked by means of the locking handle 113, the screws 116 and 113 can be tightened,and these will serve to hold the plate 114 rigidly against the block 98. The bracket 88 may be provided with graduations and a co-operating indicator marked on the block 98. This is of assistance in setting the position of the roller 92.

The mechanism just described provides a means whereby the roller 92 can be reset at any predetermined distance from the plane containing the axes of the support roller 44 and the pressure roller 48. A control roller 122 is provided on the bracket 90 opposite to the control roller 92. The mounting of these two control rollers is such that when they are moved into contact with a blank placed on the support roller 44, their lines of contact with the blank will be in the plane tangential to the support roller at the point where the blank rests on that roller. If the mill is to be used for a wide variety of rings it will be necessary to provide for vertical and/ or tilting adjustment of the control roller mountings.

'If the rings, which are to be produced on the mill, are of rectangular radial cross section, then the support roller 44, presure roller 48, and control rollers 92 and 122 should all be cylindrical. However, it is possible to roll rings which have other radial cross sections, and in fact in FIGURES 3 and 4 of the drawings, there are shown support, pressure and control rollers of shapes which would be required to produce rings of arcuate radial cross section. It will be appreciated that it is difllcult to produce tapering rings because of the tendency of the ring to creep oif the support roller, but it is possible to produce rings of chevron shaped radial cross section, so that in effect two tapering rings are produced at the same time in backto-back relationship, and it is only necessary to part the two rings after the rolling process.

In use, a ring blank which is of the usual annular shape, and has been pre-heated, is placed on the support roller 44 so that it hangs on the roller as shown in FIGURES 2 and 4 of the drawings. The two control rollers 92 and 122 are then adjusted manually until they each engage with the periphery of the blank at a distance from the plane containing the axes of the support roller and the pressure roller, which distance is given by the formula where A equals the annular cross sectional area of the blank. The control rollers are then locked in this position.

The machine can then be operated in the usual manner, that is by causing the motor 16 to rotate the support roller 44 and by setting the hydraulic circuit so that the pressure roller 48 is gradually fed down towards the support roller 44. When the pressure roller begins to nip the blank, the blank will be squeezed out of the usual manner of ring rolling until the trip lever is operated when the rolling operation will cease. Throughout the rolling process, the control rollers 92 and 122 will engage with the periphery of the blank as it is being rolled into a ring, and will thereby exercise control over the shape of the ring. It will, of course, be appreciated that if the: ring tends to distort at any time this will be rectified by the engagement of an outwardly distorted portion with one or other of the two control rollers. In practice, a blank is usually far from circular, and in these circumstances rolling may be commenced with the two control rollers 92 and 122 retracted a short distance and then gradually advanced towards the blank until they occupy the positions as described above.

It would be possible to use only one of the control rollers 92 and 122 providing it were pre-set to the correct distance given by the formula, but this would rely upon the nipping of the blank between the support roller and the pressure roller to provide the necessary reaction to the forces transmitted to the blank by the control roller in use. Alternatively it would be possible to engage both control rollers with the periphery of the blank, without equally spacing them on each side of the plane containing the axes of the support roller and the pressure roller. It would, however, be necessary to have the control rollers engaging with the blank along a tangent to the support roller, and measured along this line, the two points of engagement would have to be spaced apart by a distance equal to Neither of these alternatives would, however, be so satis factory as the symmetrical arrangement described with reference to the drawings.

Instead of mounting the rollers on horizontal axes, it will be understood that the axes of the several rollers may be vertical, in which case the rollers may be mounted on a table which may serve to support a blank being operated on.

Furthermore, whether the roller axes are horizontal or vertical, means may be provided for preventing axial expansion of the blanks during the rolling operation. For example, at least one of the rollers may have flanges for engagement with the end faces of the blank. Alternatively, freely rotatable rollers, for example tapered rollers, may be mounted with their axes substantially radial relatively to the blank for rolling engagement with one or both end surfaces of the blank.

With previously proposed ring rolling machines, mis shapen blanks have usually resulted in the rolling of rings which were far from circular. By employing the method of the present invention, it is possible to produce rings which are of acceptable accuracy both as regards radial thickness and circularity even when badly distorted blanks are used. As the rings are rolled to true or approximate circles, the grain of the metal follows the same path and after the rings have been turned to finished size, they are less liable to distortion during use than rings produced on previously known ring rolling mills.

Apart from its use in rolling rings from forged banks, it will be appreciated that the invention can be used for trueing up rings without reducing their thickness.

We claim:

1. A method of forming a ring or cylinder from a blank, comprising rotating said ring while restraining it against expansion in an axial direction, applying a rolling pressure to said ring at a first fixed point on its inner periphery, applying rolling pressure to the outer periphery of said ring at a second point radially opposed to said first fixed pressure point, moving said second pressure point relatively toward said first pressure point, and applying a control pressure to the outer periphery of said ring at at least one predetermined position on said ring which does not move relatively to said first fixed pressure point throughout the rolling process.

2. A method of forming a ring or cylinder from a blank, comprising rotating said ring while restraining it against expansion in an axial direction, applying a rolling pressure to said ring at a first fixed point on its inner periphery, applying rolling pressure to the outer periphery of said ring at a second point radially opposed to said first fixed pressure point, moving said second pressure point relatively toward said first pressure point, applying a control pressure to the outer periphery of said ring at a position which is a selected distance from a plane through said first and second pressure points which contains the axis of rotation of said ring, said distance being given by the formula wherein A equals the cross-sectional area of the blank, and holding said position fixed relative to said first pressure point during the rolling process.

3. A method of forming a ring or cylinder from a blank, comprising rotating said ring while restraining it against expansion in an axial direction, applying a rolling pressure to said ring at a first fixed point on its inner periphery, applying rolling pressure to the outer periphery of said ring at a second point radially opposed to said first fixed pressure point, moving said second pressure point relatively toward said first pressure point, applying control pressures at two positions on the outer periphery of said ring, said positions being on opposite sides of a plane through said first and second pressure points which contains the axis of rotation of said ring and being spaced apart a distance given by the formula wherein A equals the cross-sectional area of the blank, and holding said positions fixed relative to said first pressure point during the rolling process.

4. A method of forming a ring or cylinder from a blank, comprising rotating said ring while restraining it against expansion in an axial direction, applying a rolling pressure to said ring at a first fixed point on its inner periphery, applying rolling pressure to the outer periphery of said ring at a second point radially opposed to said first fixed pressure point, moving said second pressure point relatively toward said first pressure point, applying control pressures at two positions on the outer periphery of said ring, said positions being equidistant from a plane through said first and second pressure points which contains the axis of rotation of said ring, the distance of each of said positions from said plane being given by the formula wherein A equals the cross-sectional area of the blank, and holding said positions fixed relative to said first presgiven by the formula References Cited in the file of this patent UNITED STATES PATENTS 323,281 Daelen July 28, 1885 651,740 Allagnier June 12, 1900 2,120,881 Assbroicher et-al June 14, 1938 2,307,191 Bell Jan. 5, 1943 2,610,532 Heppenstall Sept. 16, 1952 2,776,585 Kendall Jan. 8, 1957 FOREIGN PATENTS 89,546 France Apr. 22, 1870' 

